The present invention relates to a method for controlling a hydraulic cylinder and control system for a work machine.
The invention will be described below in connection with a work machine in the form of a wheel loader. This is a preferred but in no way limiting application of the invention. The invention can also be used for other types of work machines (or work vehicles), such as an excavator loader (backhoe) and excavating machine.
The invention relates, for example, to controlling lifting and/or tilting cylinders for operating an implement.
A known such control system for a work machine comprises at least one hydraulic cylinder and means for controlling a communication path between the piston-rod side and piston side of the hydraulic cylinder.
It is desirable to provide a method for controlling a hydraulic cylinder that permits energy-efficient operation of a work machine comprising the hydraulic cylinder.
According to an aspect of the present invention, a method is provided for controlling a hydraulic cylinder, comprising the steps of detecting at least one operating parameter, and of variably controlling a communication path between the piston-rod side and piston side of the hydraulic cylinder on the basis of the detected operating parameter.
More specifically, the piston side of the hydraulic cylinder can be connected directly to the piston-rod side. By continually variably controlling the communication path, it is possible to control a lowering or raising movement accurately on the basis of various operating parameters in order to achieve as rapid and/or energy-efficient movement as possible. The control of the communication path preferably involves controlling a pressure on a side of the cylinder that is opposite to the side of the cylinder toward which the piston in the hydraulic cylinder is moved. In other words, when lowering the load arm as described in the embodiment shown in FIGS. 1-2, the pressure is controlled on the piston-rod side and full flow can be achieved for maximum refilling of the piston-rod side. The pressure can be adjusted between zero and the pressure on the piston side. In a corresponding way, when raising the load arm, the pressure is controlled on the piston side. The communication path is preferably controlled by means of an electrically controlled valve, whereby the drop in pressure is controlled indirectly.
It is desirable to achieve a control system, preferably for a lift function and/or tilt function, that permits energy-efficient operation.
According to an aspect of the present invention, a control system is provided for a work machine comprising at least one hydraulic cylinder and means for controlling a communication path between the piston-rod side and piston side of the hydraulic cylinder, characterized in that a line connects the piston-rod side and the piston side, and that the control means is arranged on said line and is designed to be variably adjustable between two end positions.
The hydraulic cylinder is preferably adapted to move an implement in order to perform a work function. According to a first example, the hydraulic cylinder comprises a lifting cylinder for moving a load arm which is pivotably connected to a vehicle frame, the implement being arranged on the load arm. According to a second example, the hydraulic cylinder comprises a tilting cylinder for moving the implement which is pivotably connected to the load arm.
Further preferred embodiments and advantages of the invention emerge from the following description.